review: M5c-2 review, lessons T59 and T60, and the gate-count rule

Co-Authored-By: Grok 4.6 <noreply@x.ai>

AGENTS.md

@@ -26,6 +26,8 @@ Unix sockets. You are implementing it one task at a time.
    other directory outside the repository.
 6. If you hand a task to another agent, tell it to read `AGENTS.md` and the task file itself. Do
    not pass on your own summary of either. Log what the agent did, as it did it.
+7. If HEAD already has this task's commit and a `done` row for it, stop. Do not start the task
+   again.
 
 ## Files you must never edit
 
@@ -94,6 +96,8 @@ These come from defects found in review. The evidence is in `docs/implementer-le
   does not match, look at `git diff <file>` for your own earlier edit, then stop and report; never
   anchor the edit on another line.
 - Write your log row from `git diff` after staging, naming only what the diff shows.
+- After `gate: ok`, do not run `cargo test --workspace` only to count tests. If HEAD already has
+  this task's commit and a `done` row, stop.
 
 ## The gate
 
@@ -104,7 +108,8 @@ warnings denied, all tests, cargo-deny, and the scripts in `scripts/`. Run `carg
 the gate; rustfmt decides the order of `mod` and `use` lines, not you. After you add a dependency,
 run `cargo build` once so that `Cargo.lock` is updated, then run the gate. A test count in a task
 is the passed total of `cargo test --workspace` plus one, for the ignored `end_to_end` test that
-the gate runs on its own; never run the gate again only to count.
+the gate runs on its own; never run the gate again only to count. After `gate: ok`, do not run
+`cargo test --workspace` only to count tests; the gate's total is the count.
 
 Useful while working: `cargo test -p <crate> --test <file>` runs one test file, and
 `cargo test -p <crate> <name>` runs tests whose name contains `<name>`.